Cryopreservation of people or large animals is not reversible with current technology. The stated rationale for cryonics is that people who are considered dead by current legal or medical definitions may not necessarily be dead according to the more stringent information-theoretic definition of death.
It is proposed that cryopreserved people might someday be recovered by using highly advanced technology. Those who believe that revival may someday be possible generally look toward advanced bioengineering, molecular nanotechnology, nanomedicine, or mind uploading as key technologies.
Revival requires repairing damage from lack of oxygen, cryoprotectant toxicity, thermal stress (fracturing), freezing in tissues that do not successfully vitrify, and reversing the effects that caused the patient’s death. In many cases extensive tissue regeneration will be necessary. Hypothetical revival scenarios generally envision repairs being performed by vast numbers of microscopic organisms or devices.
These devices would restore healthy cell structure and chemistry at the molecular level, ideally before warming. More radically, mind transfer has also been suggested as a possible revival approach if and when technology is ever developed to scan the memory contents of a preserved brain.
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